Magnetic alloy of high permeability



Patented May 10, 1932 I UNITED STATES PATENT OFFICE HAN S NEUMANN, OF IBERLl'N-SIEMENSSTADT, AND HEINRICH KIIHLEWEIN, OF BERLIN- MARIENFELDE, GERMANY, ASSIGNORS T SIEMENS 8c HALSKE, AKTIENGESELL- SOME, OF SIEMENSSTADT, NEAR BERLIN, GERMANY, A CORPORATION OF GER- MANY MAGNETIC ALLOY OF HIGH PERMEAIBILITY No Drawing. Application filed April 25, 1931, Serial No. 532,994, and in Germany September 28, 1929.

Our invention relates to magnetic alloys of high permeability and more particularly to iron-nickel alloys.

A number of magnetic iron-nickel alloys [l having a highpermeability for small magnetizing fields, are known. It has also already been suggestedto add cobalt in quantities exceeding 4 per cent. to these alloys to increase the permeability.

10 The. object of our invention is to increase is obtained according'to the invention with iron-nickel alloys containing to 90 per cent. of nickel, the remainder consisting of iron besides a small quantity of impurities. The highest permeability is obtained with, a

cobalt content of about 3 per cent. and a nickel content of between 70 and 85 per cent.

With an alloy containing 76.2 per cent. of r this manner the following magnetic values nickel, 20.9 per cent. of iron and 2.9 per cent. of cobalt, for example, the following values are obtained, after the alloy has been subjected to the heat treatment hereinafter described. Initial permeability 12 700 Maximum permeability 44: 200

Initial permeability 7 200. Maximum permeability 66 400 The reversible permeability is? 000 to 8 000; the permeability of this alloy increases by about 10 per cent. when the fieldv strength 1s increased from 0.00 to 0.01 gauss.

The heat treatment to obtain these maximam values of the permeability consists in that the alloys are annealed at 900 C- during an hour and then slowly cooled to about 625 C., whereupon they are quenched in the air. Through this heat treatment, very high it is still exceedingly high, being at least fivetimes higher than for iron. lViththe alloys according to our invention, therefore, a high initial permeability and besides a great constancy of the permeability is obtained.

A heat treatment particularly to be recommended, is the following:

The alloy is annealed during at least an hour at a temperature of 900 to 1 100 C. and then cooled slowly during 1 to 24 hours. The slow cooling must extend to about 200 C. The further cooling may take place slowly or quickly without the properties of the alloys being substantially influenced thereby. If the last alloy mentioned above is treated in are obtained:

Initial permeability 2 000 Reversible permeability 1 800 Maximum permeability 7 800 Within the limits 0.00 to 0.30 gauss of the field strength, the permeability increases only 10 per cent. and is, therefore, practically con-, stant in that range.

As known, the specific resistance can be increased by the addition of suitable metals, such as copper, silicon, aluminium, chromium, manganese and others. By the addition of a small quantity of silicon. the injurious influence of the carbon upon the magnetic properties may be reduced. The quantity of the said metals added to increase the specific resistance should not, however, exceed 5 per cent.

We claim as our invention:

1. A magnetic iron-nickel cobalt alloy containing 0.5 to 3.5 per cent. of cobalt, 30 to 90 per cent. of nickel, the whole of the remainder consisting of iron. 2. A,magnetic iron-nickel cobalt alloy con- 5 taining 2.9 per cent. of cobalt, 76.2 per cent. of nickel, 20.9 per cent. of iron.

3. A magnetic iron-nickel cobalt alloy con- 4 taining 1.0 per cent. of cobalt, 78.5 per cent. of nickel, 20.5 per cent. of iron.

4. A magnetic alloy which contains as essential ingredients iron, nickel and cobalt wherein the cobalt content is from 0.5 to 3.5%; the nickel content is from 30 to 90% and the iron content is from 6.5 to 69.5% of the entire iron-nickel-cobalt content.

5. A magnetic alloy, which as essential ingredients, contains iron, nickel and cobalt, the cobalt content ranging from 2.5 to 3.5%;

. the nickel content ranging from 70 to 85%; 20 and the iron content ranging from 1.5 to

6. A magnetic alloy, which as essential ingredients, contains iron, nickel and cobalt and wherein the cobalt content com rises 5 from 1 to 3.5% of the entire amount 0 iron, 7

nickel, am cobalt content.'

In testimony whereof we aflix our signatures.

HANS NEUMANN. HEINRICH KU'HLEWEIN. 

